1. Field of the Invention
The present invention involves methods and materials for coating large optical substrates with metal oxide films used in televisions and computer displays. More specifically, the methods and materials involve the use of a liquid precursor solution to deposit a corresponding magnesium oxide film on a plasma display panel.
2. Statement of the Problem
A variety of technologies are available to those who wish to build displays for electronically driven visual images. Some of these technologies include cathode ray tubes, electroluminescent displays, liquid crystal displays, plasma addressed liquid crystals, plasma display panels, vacuum fluorescent displays, and rear projection systems. Methods for producing large area displays, i.e., displays having a view-screen diagonal of greater than about fifteen or twenty inches, are associated with significantly increased process complexity and cost. Thus, not all technologies are cost-competitive when they are applied to the production of large area displays. Competitive technologies for use in the manufacture of large area displays include cathode ray tubes, plasma display panels, and rear projection systems.
Recent advances have shown that plasma display panels are the leading flat-panel technology for large area displays. It is possible to produce color plasma display panels having image quality and performance exceeding that which is obtainable from the bulkier cathode ray tubes. Rear projection systems are associated with inherent visual distortions, and these systems are also bulkier than plasma display panels. Plasma display panels may be scaled to any useful size.
Current plasma display panel research and development efforts focus on displays having view-screen diagonals ranging from about twenty to sixty inches. Large-scale prototype displays having view screen diagonals of about sixty inches have recently been produced, but low-cost manufacturing processes for large-scale plasma displays are still in the early stages of development.
Numerous problems in manufacturing development presently hinder full commercialization of large area plasma display panels. Weber et al, in Materials and Manufacturing Issues for Color Plasma Displays, MRS Bulletin, pp. 65-68 (March, 1996), describe a multitude of problems in manufacturing development for large-area color plasma display panels. These problems include visual distortion induced by barrier rib warpage and screen stretch during firing, visual distortion induced by a high firing temperature for dielectric glass, problems with existing magnesium oxide deposition techniques, phosphor degradation, and poor luminance efficiency. Dimensional changes as small as 0.1% are known to induce visual distortion through corresponding problems in registration of the plasma display panel electrodes. The Weber et al article indicates that these problems have not yet been solved.
State-of-the-art color plasma displays include a thin layer of magnesium oxide coating the interior surface of a front glass panel and a plurality of cathodes. This magnesium oxide layer is needed to protect the cathodes and eliminate erosion of the dielectric glass. Current practices for depositing this layer include the electron-beam evaporation of a magnesium oxide target in a high temperature vacuum chamber. The electron beam evaporation method is time-consuming and costly, but no suitable alternative is known. The Weber et al article, at page 67, indicates that possible alternative solutions to electron beam evaporation include sputtering and screen printing; however, the article also indicates that no satisfactory high-volume, low-cost alternative to electron beam deposition has yet been found.
There exists a true need for a high-volume, low-cost method of depositing magnesium oxide on large area plasma displays.